562 GLACIAL FOEMATIONS OF ERIE AND OHIO BASINS. 



surface till. A laminated structure was observed in a, few places, and it is 

 not improbable that it is a subaqueous deposit, made perhaps during the 

 retreat of the ice sheet from the Wabash to the St. Marys nioi'aine. If 

 the retreat was such as to block the western outlet, lakes may for a time 

 have been held between the ice sheet and the Wabash moraine. No 

 exposures were afforded by which determinations of the thickness of the 

 deposit could be made, but, judging from well sections reported, it is at 

 most but a few feet. 



The forest on this plain contains beech, maple, elm, ash, etc., with but 

 little oak, and in this respect the area presents a striking contrast to the 

 oak-covered moraine. 



In northern Allen and Dekalb counties this moraine is separated from 

 the Fort Wayne only by the narrow valley of the St. Joseph River, and 

 the phenomena along this river valley are discussed in connection with the 

 latter moraine. 



OUTER BORDER PHENOMENA. 



From near Mansfield, Ohio, westward to the old lake outlet there is a 

 plain similar to the plain on the inner border, just described, having a deep 

 black soil, heavy forest, and a clay subsoil which appears to be, in part at 

 least, of subaqueous origin. There is remarkably little coarse material 

 along valleys, and glacial outwash seems to have been weak. Gravel 

 deposits occur along the Wabash River below Blufifton, Ind., but were not 

 observed above that city. Their relation to the moraine was not satisfac- 

 torily determined. In southern Dekalb and northern Allen counties, lud., 

 a gravel plain extends from Big Cedar Creek southwestward past Hunter- 

 town to the head of Eel River. A portion of it is dry and sandy, but much 

 of it is poorly drained and is known as the " Huntertowu marshes." It 

 appears to have been a line of discharge for the waters of the ice sheet at 

 the time the Wabasli moraine was forming. The ice sheet probably had 

 at that time a line of discharge down the old lake outlet to the Wabash, 

 but subsequent erosion has swept the valley so clean as to remove such 

 evidence of discharge as may ha^•e existed. 



Eastward from Mansfield the outer border district presents much 

 variation in features, and a more detailed description seems necessary than 

 is required for the smooth district to the west. The features of the uplands 

 lying south of the eastern part of this moraine are discussed in connection 



